The standards that have been developed for digital versatile disks (DVDs) define many features that were not available in previous standard video technologies, such as VHS tape and laser disc. Such additional features include the ability to allow the user to interact with the playback of DVD audio/visual (A/V) content to customize the presentation of the DVD A/V content for the user's preferences. The author of the DVD A/V content, however, must enable many of these features in the original production of the DVD A/V content for the features to be available to the user. For example, the author may choose to incorporate subtitles in DVD A/V content, and the user can choose which language, if any, in which to view the subtitles. An author may also re-film or reedit some scenes of a motion picture for different purposes, such as to achieve any desired rating by the Motion Picture Association of America (e.g. NC-17, R, PG-13, PG or G), or to change the story or ending. The author may then include each different version of the scenes in the DVD A/V content with formatting for “parental” control which causes the playback of the motion picture to branch between scenes so as to present only the version with the desired rating. The user may select which version or which scenes to view. A DVD A/V content author may also shoot some scenes of a motion picture from multiple angles and incorporate all of the angles, up to nine angles, in the DVD A/V content for the user to select which angle of the scene to view. Blocks of digital data for the angles are interleaved together onto the DVD disk so that the playback can branch between scenes with seamless A/V playback.
Playback using any of the above features typically requires complete playback of the entire DVD A/V content with options for pausing, fast forwarding, fast reversing, etc. DVD players also typically provide for branching to specific points within the DVD A/V content to begin playback at these points, such as at the start of chapters or scenes. DVD players, however, do not permit specifying an actual address within the DVD bitstream (the compressed, DVD-encoded digital data that represents the DVD content) for a location to start the playback. Recording in the DVD format is a feature that is typically not available in DVD players, since DVD recording technology is expensive. An author of DVD content, therefore, performs all authoring and editing tasks on the DVD content prior to storing the completed DVD bitstream on media. Generally, DVD A/V content is encoded in the MPEG-2 (Motion Picture Expert Group) format, so editing features typically provide cut, paste and other edit commands for creating MPEG-2 files prior to creating a DVD disk on which is stored the DVD content. Such editing features are not provided in DVD players for playing back DVD content from the DVD disk, since the users only need to view the DVD A/V content, not create it.
DVD A/V content is generally decoded by a DVD player into conventional A/V content for presentation on a conventional display (e.g. a television). It is generally possible, therefore, to play back the DVD A/V content and record the conventional A/V content generated thereby. For example, the DVD A/V content may be played back to a video cassette recorder (VCR), which records the conventional A/V content as it would be played back on a conventional television.
To record only a short segment of the DVD A/V content as it is being played back, however, requires a user to view the real-time playback of the DVD content and to start and stop the VCR recording at the desired points during the playback. Capturing the exact desired segment of the playback is, thus, an inexact or hit-or-miss situation.
Additionally, the A/V content recorded by a conventional VCR contains only the audio and visual material that is played back to the television. Any other available features, such as the subtitles, the parental features, the multiple angles, etc., cannot be simultaneously recorded by the VCR, since they cannot all be played back simultaneously and the VCR can only record one stream of A/V content at a time. In other words, to record the DVD A/V content with all of the desired features, the DVD A/V content must be played back and recorded several times, each time with a different one of the desired features selected. In doing so, however, the enhanced capabilities provided by these other features are absent in the recorded A/V content. Thus, the user can play back the recorded A/V content only as it was recorded, without the user-selection of the DVD features available in the original DVD content. Also, the screen resolution (i.e. the horizontal lines of resolution, or the horizontal-by-vertical pixel resolution) of the recorded A/V content depends on the resolution of the played back video, which, for conventional television, is less than the full resolution capabilities of the DVD standards. Thus, some of the quality of the DVD A/V content is lost. Furthermore, since the VCR does not record the exact digital data from the original DVD content, but only an analog approximation thereof, such recording is invariably “lossy” by nature (i.e. naturally loses some detail or quality in the recording).
It is with respect to these and other background considerations that the present invention has evolved.